Abstract

Liveweight changes were measured when 210 yearling Brahman crossbred steers (396kg mean initial liveweight) were held in yards and fasted (no feed and water) for 12, 24, 48 or 72 hours. The first fast was followed by a 48h recovery period on water (12W, 24W, 48W and 72W) or water plus hay (48F and 72F), and then a second fast of 12h. Finally, the steers returned to pasture for 16 days. The steers lost weight most rapidly during the initial 12h of the first fast. After 12, 24, 48 and 72h they had lost 23, 30, 46 and 57kg of their initial liveweight (P < 0.01). All steers recovered weight rapidly when given access to water or water plus feed, particularly during the first 6h. As a consequence, the range in liveweight of 34kg between the treatments at the end of the first fast was reduced to as little as 9 and 10kg after 12 and 18h, respectively. Twelve hours after the recovery period had commenced, all steers were again losing weight. At the end of this period the range in liveweight was 17kg ; losses in toto being 33kg (12W) to 50kg (72W). At the end of the second fast these losses had increased. Net losses in liveweight were 40, 50, 56 and 58kg for the 12W, 24W, 48W and 72W steers compared with 46 and 44kg for the 48F and 72F steers, respectively (P < 0.01). After 16 days on pasture, the 12W steers had regained their initial liveweight whereas the 72W steers were 10 kg lighter (P < 0.01 ). The implications for selling of cattle on liveweight through saleyards are discussed in terms of present procedures and the imposition of statutory fasting periods. An alternative system is proposed.